Risk Group Classification for Infectious Agents

In many countries, including the United States, infectious agents are categorized in risk groups based on their relative risk. Depending on the country and/or organization, this classification system might take the following factors into consideration:

1. WHO Classification of Infective Microorganisms by Risk Group (2004)
WHO Basis for Risk Grouping: Each country classifies the agents in that country by risk group based on pathogenicity of the organism, modes of transmission and host range of the organism. These may be influenced by existing levels of immunity, density and movement of host population presence of appropriate vectors and standards of environmental hygiene.

Availability of effective preventive measures. Such measures may include: prophylaxis by vaccination or antisera; sanitary measures, e.g. food and water hygiene; the control of animal reservoirs or arthropod vectors; the movement of people or animals; and the importation of infected animals or animal products.

Availability of effective treatment. This includes passive immunization and post-exposure vaccination, antibiotics, and chemotherapeutic agents, taking into consideration the possibility of the emergence of resistant strains. It is important to take prevailing conditions in the geographical area in which the microorganisms are handled into account. Note: Individual governments may decide to prohibit the handling or importation of certain pathogens except for diagnostic purposes.

WHO Risk Group 1 (no or low individual and community risk). A microorganism that is unlikely to cause human disease or animal disease

WHO Risk Group 2 (moderate individual risk, low community risk). A pathogen that can cause human or animal disease but is unlikely to be a serious hazard to laboratory workers, the community, livestock or the environment. Laboratory exposures may cause serious infection, but effective treatment and preventative measures are available and the risk of spread of infection is limited.

WHO Risk Group 3 (high individual risk, low community risk). A pathogen that usually causes serious human or animal disease but does not ordinarily spread from one infected individual to another. Effective treatment and preventive measures are available.

WHO Risk Group 4 (high individual and community risk). A pathogen that usually causes serious human or animal disease and that can be readily transmitted from one individual to another, directly or indirectly. Effective treatment and preventive measures are not usually available.

The following classification is based on the pathogenicity of the agent, the mode of transmission and host range of the agent, the availability of effective preventive measures and the availability of effective treatment.

group 1 (low individual and community risk). A microorganism that is unlikely to cause human, plant or animal disease.

group 2 (moderate individual risk, limited community risk). A pathogen that can cause human, animal or plant disease but is unlikely to be a serious hazard to laboratory workers, the community, livestock or the environment. Laboratory exposures may cause infection, but effective treatment and preventive measures are available and the risk of spread is limited.

group 3 (high individual risk, limited community risk). A pathogen that usually causes serious human or animal disease and may present a serious hazard to laboratory workers. It could present a risk if spread in the community or the environment, but there are usually effective preventive measures or treatment available.

group 4 (high individual and community risk). A pathogen that usually produces life-threatening human or animal disease represents a serious hazard to laboratory workers and is readily transmissible from one individual to another. Effective treatment and preventive measures are not usually available.

3. Canadian Laboratory Safety Guidelines (2004; list not available)
Inherent risks of a pathogen made on basis of factors such as severity of disease caused, routes of infection, virulence and infectivity takes into account existence of effective therapies, possibilities for immunization, presence of vectors, quantity of agent and whether agent is indigenous to Canada, possible effects on other species, including plants, or possible economic environmental effects.

Risk Group 1 (low individual and community risk). Any biological agent that is unlikely to cause disease in healthy workers or animals.

Risk Group 2 (moderate individual risk, limited community risk). Any pathogen that can cause human disease, but under normal circumstances is unlikely to be a serious hazard to laboratory workers, the community, livestock or the environment. Laboratory exposures rarely cause infection leading to serious disease, effective treatment and preventive measures are available and the risk of spread is limited.

Risk Group 3 (high individual risk, low community risk). Any pathogen that usually causes serious human disease, or can result in serious economic consequences but does not ordinarily spread by casual contact from one individual to another, or that causes disease treatable by antimicrobial or antiparasitic agents.

Risk Group 4 (high individual and community risk). Any pathogen that usually produces very serious human disease, often untreatable, and may be readily transmitted from one individual to another, or from animal to human or vice-versa, directly or indirectly, or by casual contact.

4. European Economic Community (2000)
Directive 2000/54/EC and Directive 90/679/EEC (adopted 20 November, 1990; revised 18 September 2000) on the protection of workers from risks related to exposure to biological agents at work provides for the Classification of biological agents into four infection risk groups on the basis of the following criteria:

Group 1 biological agent means one that is unlikely to cause human disease.

Group 2 biological agent means one that can cause human disease and might be a hazard to workers; it is unlikely to spread to the community; there is usually effective prophylaxis or treatment available.

Group 3 biological agent means one that can cause severe human disease and present a serious hazard to workers; it may present a risk of spreading to the community, but there is usually effective prophylaxis or treatment available.

Group 4 biological agent means one that causes severe human disease and is a serious hazard to workers; it may present a high risk of spreading to the community; there is usually no effective prophylaxis or treatment available.

Risk Group 1 (RG1) Agents that are not associated with disease in healthy adult humans. Includes a list of animal viral etiologic agents in common use.

Risk Group 2 (RG2) Agents that are associated with human disease which is rarely serious and for which preventive or therapeutic interventions are often available.

Risk Group 3 (RG3) Agents that are associated with serious or lethal human disease for which preventive or therapeutic interventions may be available (high individual risk but low community risk).

Risk Group 4 (RG4) Agents that are likely to cause serious or lethal human disease for which preventive or therapeutic interventions are not usually available (high individual risk and high community risk).

Biosafety Level 3 (BSL 3): indigenous or exotic agents which may cause serious or potentially lethal disease as a result of exposure by the inhalation route (applicable to clinical, diagnostic, teaching, research or production facilities)

3.National Institutes of Health. 2002. NIH Guidelines for Research Involving Recombinant DNA Molecules (NIH Guidelines) 59 FR 34496 (July 5, 1994), as amended. The current amended version of the NIH Guidelines can be accessed at: http://oba.od.nih.gov/rdna/nih_guidelines_oba.html

4.European Union. 2000. Directive 2000/54/EC of the European Parliament and of the Council of 18 September 2000 on the protection of workers from risks related to exposure to biological agents at work.(seventh individual directive within the meaning of Article 16(1) of Directive 89/391/EC Official Journal of the European Communities L262/21. October 17,2000